The present invention relates to a movable cover or roof for covering crops such as orchard trees and protecting them from frost damage.
Frost can kill or injure crops and is an especially grave danger in orchards where the fruit itself is exposed during periods of cold weather. Methods of protecting crops against frost include smudge pots, university return stack heaters, liquid fuel heaters and wind machines all of which consume expensive fuel as well as portable covers which act to retain warm air or to block cold drafts. Portable covers may be used to cover individual plants or all the plants on a plot of land to retain warm air and to block cold air radiation.
Protective coverings for agricultural plots found in the prior art include movable protective covering for orchards disclosed in U.S. Pat. No. 1,106,624 to Cadwallader et al. In Cadwallader a framework of static rigging is formed by vertical uprights, carrying guy wires. A flexible fabric covering is extended over the framework by turning large drums located at opposite ends of the framework that operate as take-up reels for the fabric and for the cable which draws the fabric across the crossbars and rollers and along the support wires.
Movable fabric panels are found in U.S. Pat. No. 2,051,643 to Morrison which discloses a cloth house for protecting plants. In Morrison an insect-proof fabric house composed of numerous strips joined edge to edge is supported over a framework of posts, guy wires and supporting cables. Some fabric joints incorporate weight supporting wires and the lowermost edges of the fabric are held fast to a framework by wires within the fabric edge which connect to gourmets located on baseboards of the framework. Morrison's cloth house was improved by adding the transverse cords disclosed in U.S. Pat. No. 2,143,659 to Morrison to the top surface of the house.
Another form of portable plant protection is disclosed in U.S. Pat. No. 3,100,950 to Heuer in which a cover is suspended between or across rows of posts. The cover can be folded back by manually drawing it back in a direction along the row.
While the devices disclosed in the identified patents and other devices in the prior art were satisfactory for their intended use, they were not intended to be adapted for use with lightweight synthetic materials.
Thus there existed a need for a plant protecting cover which could selectably be placed over the crops to protect them or be withdrawn to allow light and water to enter the orchard. Ideally the cover should be easily operated by one man, should be able to be quickly opened or retracted, should be relatively inexpensive to fabricate and should be able to be exposed to the elements for a long period of time without damage. The present invention fulfills these requirements.